Background Sulfonamide hypersensitivity has a high incidence in HIV infection and correlates with low CD4+ counts, but the mechanisms are not understood. The aims of this study were to determine whether trimethoprim/sulfamethoxazole (TMP/SMX) led to SMX adduct formation, immunogenicity, or signs of drug hypersensitivity in SIV-infected rhesus macaques, and whether differences in antioxidants, pro-inflammatory mediators, or SMX disposition were predictive of drug immunogenicity. Methods Nine macaques chronically infected with SIVmac239 and 7 non-infected controls were studied. Baseline blood ascorbate, glutathione, IFN-γ, LPS, sCD14, and cytochrome b5 reductase measurements were obtained, macaques were dosed with TMP/SMX (120 mg/kg/day p.o. for 14 days), and SMX metabolites, lymph node drug adducts, drug-responsive T cells, and anti-SMX antibodies were measured. Results Four of 9 of SIV-positive (44%), and 3 of 7 SIV negative (43%) macaques had drug-responsive T cells or antibodies to SMX. Two macaques developed facial or truncal rash; these animals had the highest levels of lymph node drug adducts. Antioxidants, pro-inflammatory mediators, and SMX metabolites were not predictive of drug immunogenicity; however, the Mamu DRB1*0401/0406/0411 genotype was significantly over-represented in immune responders. Conclusions Unlike other animal models, macaques develop an immune response, and possible rash, in response to therapeutic dosages of TMP/SMX. Studying more animals with CD4+ counts < 200 cells/µl, along with moderately restricted ascorbate intake to match deficiencies seen in humans, may better model the risk of SMX hypersensitivity in HIV-infection. In addition, the role of Mamu-DRB1 genotype in modeling drug hypersensitivity in retroviral infection deserves further study.

HIV‐infected patients show a markedly increased risk of delayed hypersensitivity (HS) reactions to potentiated sulfonamide antibiotics (trimethoprim/sulfamethoxazole or TMP/SMX). Some studies have suggested altered SMX biotransformation in HIV infection, but hepatic biotransformation pathways have not been evaluated directly. Systemic lupus erythematosus (SLE) is another chronic inflammatory disease with a higher incidence of sulfonamide HS, but it is unclear whether retroviral infection and SLE share risk factors for drug HS. We hypothesized that retroviral infection would lead to dysregulation of hepatic pathways of SMX biotransformation, as well as pathway alterations in common with SLE that could contribute to drug HS risk. We characterized hepatic expression profiles and enzymatic activities in an SIV‐infected macaque model of retroviral infection, and found no evidence for dysregulation of sulfonamide drug biotransformation pathways. Specifically, NAT1,NAT2,CYP2C8,CYP2C9,CYB5R3,MARC1/2, and glutathione‐related genes (GCLC,GCLM,GSS,GSTM1, and GSTP1) were not differentially expressed in drug naïve SIVmac239‐infected male macaques compared to age‐matched controls, and activities for SMX N‐acetylation and SMX hydroxylamine reduction were not different. However, multiple genes that are reportedly over‐expressed in SLE patients were also up‐regulated in retroviral infection, to include enhanced immunoproteasomal processing and presentation of antigens as well as up‐regulation of gene clusters that may be permissive to autoimmunity. These findings support the hypothesis that pathways downstream from drug biotransformation may be primarily important in drug HS risk in HIV infection.

HIV infected patients have a high risk of hypersensitivity (HS) reactions to trimethoprim/ sulfamethoxazole (TMP/SMX). To understand this, simian immunodeficiency virus (SIV)‐infected rhesus macaques were used to explore possible metabolic and immunologic risk factors. We hypothesized that pathways affecting sulfamethoxazole disposition might be altered by SIV infection. Liver biopsies were obtained from three SIVmac239‐infected male macaques and three non‐infected controls for a whole‐transcript gene expression array experiment. 138 genes were significantly differentially expressed (P < 0.005), with 114 genes up‐regulated and 24 genes down‐regulated. No sulfonamide biotransformation genes, to include CYP2C8, CYP2C9, CYB5R3, NAT2, or glutathione synthetic pathways, were differentially expressed. However, multiple genes involved in antigen processing, to include ubiquitination and proteasomal degradation, were significantly up‐regulated up to10‐fold. Genes involved in antigen presentation were up‐regulated by 1.7‐2.3 fold (P < 0.003). These preliminary data suggest that acquired risk of sulfonamide HS in human retroviral infection may not be due to changes in drug biotransformation, but in the antigen processing and presentation, primarily ubiquitination. Funded by R01 GM100784.

HIV infected patients have a high risk of hypersensitivity (HS) reactions to trimethoprim/sulfamethoxazole (TMP/SMX). To understand this, simian immunodeficiency virus (SIV)‐infected rhesus macaques were used to explore possible metabolic and immunologic risk factors. SIVmac239‐infected male macaques and non‐infected controls were administrated TMP/SMX (120 mg/kg/day) for 14 days. Prior to dosing, plasma was assayed for antioxidants and cytokines, needle liver biopsies were collected for expression arrays, and PBMC were isolated for in vitro toxicity assays. After treatment, urine was collected for SMX metabolites, plasma was analyzed for anti‐drug antibodies, PBMC were tested for drug specific T cells, and lymph node and plasma were assayed for drug adducts. 7 SIV‐infected and 4 control animals have been treated to date. Baseline plasma ascorbate and red cell glutathione were not significantly different between groups. SMX hydroxylamine was significantly more toxic towards PBMC from SIV‐infected animals (37%) compared to controls (2%; P = 0.04). One SIV‐infected monkey developed an erythematous rash on day 7, and was positive for anti‐SMX antibodies; 3 additional monkeys showed T cells reactive to SMX‐nitroso or TMP. These preliminary data suggest that TMP/SMX is immunogenic in macaques as in humans, and that signs consistent with sulfonamide HS may be possible in this model. Funded by R01 GM100784.